The singer considers the father's reticence to bless a their relation to be a sign of rudeness, although we must remember the singer is an unreliable narrator and only gives his own point of view.
If the listener were privy to the father's point of view it is likely that there are reasons why he would not want his daughter marrying the singer (for example, the singer's opinion that anyone who opposes him only does so out of rudeness, rather than accepting any blame for his own actions that might make him an unacceptable candidate for marriage).
There also is no mention of the daughter's opinion about any of this, and based on lines like "I'm gonna have her for the rest of my life" the singer may be overly possessive. The daughter may not want to marry someone so backwards as to think he can own her, and the singer may not have accepted this rejection from her. Perhaps the song is his attempt to go over her head and "purchase" her from her father, whom he considers her original owner. In this case, the father is carrying out his daughter's wishes by continuing to reject the singer, and the singer is so oblivious that he still only considers that the father is simply being "rude."